Transistor characteristics of monolithic GaAs/ AlGaAs three-terminal junctions are studied at room temperature. It is found that the channel is controlled by the center branch, although considerable leakage currents flow into the junction. Large current gain, up to 60, is observed. Furthermore, a maximum differential-voltage gain up to values of −30 is demonstrated. The frequency dependence of the rectified output provides a cutoff frequency of 4 GHz.

Direct current and alternating current characteristics of three-terminal nanojunctions (TTJs) are studied at room temperature. The TTJs are based on a modulation-doped GaAs∕AlGaAs heterostructure and were structured by applying mask techniques and wet chemical etching. Devices with lateral dimensions of a few tens of nanometers and with narrow gold contacts were fabricated and transistor characteristics with maximum transconductance values exceeding 100μA∕V are demonstrated. By analyzing the scattering parameters of the TTJs, power gain up to 1.5GHz is observed. This gigahertz amplification is related to the implemented narrow gold contacts which control the quantum capacitance of the electron reservoirs.

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The authors studied the role of gate leakage on the drain current in a monolithic, unipolar GaAs∕AlGaAs heterostructure based on three contacts leaky coupled to each other. Two in-plane barriers, each defined by a row of etched holes in a two-dimensional electron gas, separate the leaky gate from the central drain and the drain from the source. A pronounced decrease of the drain current sets in when the gate starts to leak associated with the space charge injected from the leaky gate.

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